The broad, long-term goals of this study are to evaluate whether longer course antibiotic therapy for women at-risk for subclinical PID prevents subsequent infertility better than currently used short course antibiotic regimens for lower genital tract infections. Subclinical pelvic inflammatory disease (PID) is an important yet overlooked cause of infertility, responsible for more cases of post-infectious tubal infertility than acute PID. Subclinical PID is present in 25% of women with gonorrhea or chlamydia, and one in seven women with bacterial vaginosis, despite the absence of symptoms of acute PID. Most importantly, there is a doubling in infertility among women with subclinical PID compared to women without PID. Current treatment strategies for cervicitis and vaginitis do not address ongoing upper genital tract inflammation. Our hypothesis is that the preservation of fertility is greater among women with subclinical PID treated with a long-course antibiotic regimen compared to women receiving standard single-dose regimens for uncomplicated lower genital tract infections. The proposed application describes a randomized, double-blind, comparative phase III clinical trial studying a novel treatment regimen that incorporates azithromycin, an antimicrobial with potent immunomodulatory properties, on fertility outcomes in women at-risk for post-infectious fallopian tube damage. The specific aims are to 1) compare fertility rate of women with subclinical PID receiving two weeks of broad-spectrum antibiotic therapy with the fertility rate of women with subclinical PID receiving single-dose antibiotic regimen, 2) determine whether the resolution of endometritis is more common in women treated with the enhanced antimicrobial regimens utilized for acute PID compared to currently recommended single-dose regimens for lower genital tract infections, 3) characterize the inflammatory response in the lower genital tract in women with and without subclinical PID, and 4) evaluate whether women with subclinical PID have evidence of fallopian tube inflammation. During this study, very real public health questions will be asked and answered which will affect the way that lower genital tract infections are routinely managed, potentially enhancing fertility among American women.